Wood fibre based direct pressed laminated flooring (DPL) usually comprises a core of a 6-12 mm fibre board, a 0.2 mm thick upper decorative surface layer of laminate and a 0.1-0.2 mm thick lower balancing and/or protective layer of laminate, plastic, paper or like material.
The surface layer of a laminate floor is characterized in that the decorative and wear properties are generally obtained with two separate layers one over the other. The decorative layer is generally a printed paper and the wear layer is a transparent overlay paper, which comprises small aluminium oxide particles.
The printed decorative paper and the overlay are impregnated with melamine formaldehyde resin and laminated to a wood fibre based core under heat and pressure. The balancing layer is used to keep the panel flat after production and when the panel is exposed to variations in moisture conditions that cause the surface layer to swell and shrink.
Recently new “paper free” Wood Fibre Floor (WFF) types have been developed with solid surfaces comprising a substantially homogenous mix of fibres, binders and wear resistant particles.
The wear resistant particles are preferably aluminium oxide particles, the binders are preferably thermosetting resins such as amino resins and the fibres are preferably wood based. Other suitable wear resistant materials are for example silica or silicon carbide. In most applications decorative particles such as for example colour pigments are included in the homogenous mix. In general all these materials are preferably applied in dry form as a mixed powder on a HDF core and cured under heat and pressure to a 0.1-1.0 mm solid layer.
Several advantages over known technology and especially over conventional laminate floorings can be obtained:                The wear resistant surface layer, which is a homogenous mix, can be made much thicker and a wear resistance is achieved, which is considerably higher.        New and very advanced decorative effects can be obtained with deep embossing and by separate decorative materials, which can be incorporated into the homogenous surface layer and coordinated with the embossing.        An increased impact resistance can be reached with a homogenous surface layer, which is thicker and has a higher density.        The homogenous surface layer can comprise particles that have a positive impact on sound and moisture properties.        Production costs can be reduced since low cost and even recycled materials can be used and several production steps can be eliminated.        
Powder technology is very suitable to produce solid decorative surface layer, which are much thicker than conventional laminate surface layers. Such solid powder based layers create a much higher tension on the panel when they shrink (or swell) during curing and balancing is a problem. It is therefore difficult to produce a panel with a thick and a high quality surface, which is also well balanced after pressing as well as stable and flat in variable moisture conditions.